Vehicles may be configured with a hybrid propulsion system that utilizes at least two different sources of torque for propelling the vehicle. As one non-limiting example, a hybrid propulsion system for a vehicle may be configured as a hybrid electric vehicle (HEV), wherein an electric motor and an internal combustion engine may be selectively operated to provide the requested propulsive effort. Similarly, during deceleration of the vehicle, the electric motor and engine can be selectively operated to provide vehicle driveline braking in order to recapture kinetic energy of the vehicle. In this way, vehicle efficiency may be increased.
As described by U.S. Pat. No. 6,890,283, the engine may be disconnected from the drive wheels of the vehicle during deceleration by disengaging the transmission. By reducing engine braking during vehicle deceleration, a greater amount of energy may be recaptured by the motor.
The inventors of the present disclosure have recognized a disadvantage with the above approach. In particular, during some conditions, the motor may not be able to provide sufficient driveline braking torque. Therefore, engine braking can be provided in combination with the motor to provide the desired driveline braking torque. However, operating the engine to supplement driveline braking in addition to the motor may reduce the level of energy recaptured during the braking event.
As another approach, the inventors herein have provided a hybrid propulsion system for a passenger vehicle, comprising at least one drive wheel; a first motor coupled to the drive wheel; a second motor; a transmission including a first end coupled to the drive wheel and a second end coupled to the second motor; and a control system configured to control operation of the first and second motor to each provide vehicle braking torque, wherein transmission state is adjusted to control an amount of braking torque provided by the engine in response to an amount of braking torque provided by the first motor and an amount of braking torque provided by the second motor. In this way, a first motor and a second motor may be coordinated to provide sufficient vehicle braking, and the state of the transmission may be adjusted to facilitate the distribution of braking torque between the motors and engine, thereby improving driver feel during deceleration.
As yet another approach described herein, the control system may be configured to vary a relative level of electrical energy generated by the first motor and the second motor in response to an operating condition to generate vehicle braking. In this way, energy recapture during vehicle deceleration may be selectively performed by the first motor, second motor, or both motors while considering operating conditions such as the state of the transmission operatively coupled between the motors, a condition of the energy storage device, and/or the speed of the engine, among others.
It should be appreciated that the various concepts that have been provided in the Background and Summary are non-limiting examples and that these and other approaches will be described in the Detailed Description in greater detail. Additionally, the various approaches described herein and the claimed subject matter are not necessarily limited to addressing the above mentioned issues.